Clinical Biochemistry Practice Questions

Q: A 5-year-old child presents with symptoms of genu varum and wrist enlargement. Which one of the following biochemical measures would be most likely to be elevated in this patient?

Alkaline phosphatase. ***Alkaline phosphatase*** - In **rickets**, which is characterized by **genu varum** (bowed legs) and **wrist enlargement**, there is defective bone mineralization. Osteoblasts attempt to compensate for this defect by producing more unmineralized osteoid, leading to increased activity and release of **alkaline phosphatase**. - **Alkaline phosphatase (ALP)** is a marker of **osteoblast activity** and bone formation, and its elevation reflects the body's attempt to lay down new bone, even if it's unmineralized. *Calcium* - In **nutritional rickets** (the most common form), **serum calcium levels** are often low or normal-to-low due to inadequate intake or absorption of calcium and vitamin D. - The body tries to maintain normal calcium levels through **secondary hyperparathyroidism**, which mobilizes calcium from bones but also further impairs mineralization. *Ferritin* - **Ferritin** is a protein that stores iron and is a marker for **iron stores** in the body. - Iron deficiency anemia is a separate condition and is not directly related to the bone deformities seen in rickets; therefore, ferritin would not typically be elevated in this context. *Phosphorus* - In **nutritional rickets**, **serum phosphorus levels** are typically low due to impaired intestinal absorption and increased renal excretion, often exacerbated by secondary hyperparathyroidism. - Phosphorus is crucial for bone mineralization, and low levels contribute to the pathogenesis of rickets.

Q: Which hemoglobin has diagnostic value in diabetes mellitus?

HbA1c. ***HbA1c*** - **Glycated hemoglobin (HbA1c)** measures the average blood glucose levels over the past 2-3 months. - It is used to **diagnose diabetes mellitus**, monitor glycemic control, and assess the risk of complications. *HbA* - **Hemoglobin A (HbA)** is the most common adult hemoglobin, comprising about 95-98% of total hemoglobin. - It does not directly provide information about **long-term glycemic control**. *HbF* - **Fetal hemoglobin (HbF)** is the predominant hemoglobin during fetal life and declines after birth. - While persistence of HbF can affect HbA1c measurements (leading to falsely low values), it is **not used diagnostically for diabetes**. *HbS* - **Hemoglobin S (HbS)** is an abnormal hemoglobin variant responsible for **sickle cell anemia**. - It is crucial for diagnosing sickle cell disease but has **no diagnostic value for diabetes mellitus**.

Q: Which of the following biochemical markers is NOT elevated in a child presenting with jaundice, icterus, pruritus, and clay-colored stools?

Glutamate dehydrogenase. ***Glutamate dehydrogenase*** - **Glutamate dehydrogenase (GLDH)** is an enzyme primarily found in the mitochondria of hepatocytes and is a marker of **hepatocellular necrosis**. - In a presentation dominated by **cholestasis** (jaundice, pruritus, clay-colored stools), GLDH is typically not elevated; rather, enzymes indicative of bile duct obstruction would be. *Alkaline phosphatase* - **Alkaline phosphatase (ALP)** is an enzyme found in the bile duct epithelium and is significantly elevated in **cholestatic conditions**, such as bile duct obstruction. - Its presence in high levels is a strong indicator of an issue with bile flow. *Gamma glutamyl transpeptidase* - **Gamma-glutamyl transpeptidase (GGT)** is a microsomal enzyme found in liver cells and bile duct epithelium, with very high sensitivity for **cholestatic liver disease**. - Its elevation along with ALP helps confirm a cholestatic pattern of liver injury. *5' nucleotidase* - **5' nucleotidase (5'-NT)** is an enzyme found in the cell membranes of hepatocytes and bile duct cells. - It is considered a more **specific marker for cholestasis** than ALP, as it is not elevated in bone diseases or pregnancy.

Q: Urobilinogen levels in obstructed jaundice due to gallstones will be:

Completely absent. ***Completely absent*** - In **obstructive jaundice**, **bile flow** from the liver to the intestine is blocked, preventing **bilirubin** from reaching the gut. [1] - Since **urobilinogen** is formed in the intestines from bilirubin by bacterial action, its absence in the gut means it cannot be reabsorbed and excreted, leading to its complete absence in urine and feces. [1] *Significantly elevated* - This would typically occur in conditions causing **hemolysis** or **hepatocellular damage**, where large amounts of bilirubin are processed by the liver and then passed into the intestine. [1] - In such cases, increased bilirubin reaching the gut leads to increased urobilinogen formation and subsequent high excretion. *Mildly elevated* - A mild increase might be seen in cases of incomplete obstruction or mild liver dysfunction, where some bilirubin still reaches the intestine. - This level is not consistent with the complete blockage seen in **obstructive jaundice** from **gallstones**. *Unchanged* - This would imply that the normal process of bilirubin metabolism and urobilinogen formation is unaffected. - In **obstructive jaundice**, the very definition involves a disruption of this pathway, making an unchanged level highly unlikely. [1]

Q: In a primary health care setting, which anticoagulant combination is recommended for sending blood samples for accurate blood glucose estimation?

Potassium oxalate + sodium fluoride. ***Potassium oxalate + sodium fluoride*** - This combination is crucial for **accurate glucose measurement** because **sodium fluoride prevents glycolysis** (glucose breakdown by red blood cells) by inhibiting enolase. - **Potassium oxalate** acts as an **anticoagulant** by precipitating calcium, preventing clotting without interfering with glucose stability. *EDTA (Ethylenediaminetetraacetic acid)* - While EDTA is a common **anticoagulant** that works by chelating calcium, it does not prevent **glycolysis**. - If glucose estimation is delayed, EDTA tubes will show **falsely low glucose levels** due to red blood cell metabolism. *Heparin (Unfractionated Heparin)* - **Heparin** is an anticoagulant that inhibits thrombin, but it also **does not prevent glycolysis**. - Samples collected in heparin tubes will experience **glucose degradation** over time, leading to inaccurate results if not processed immediately. *Potassium oxalate (alone)* - **Potassium oxalate** acts as an **anticoagulant**, but it **does not prevent glycolysis**. - Therefore, without a glycolytic inhibitor like sodium fluoride, glucose levels will **decrease over time** after blood collection.

Question 1

A 5-year-old child presents with symptoms of genu varum and wrist enlargement. Which one of the following biochemical measures would be most likely to be elevated in this patient?

Accepted Answer

Alkaline phosphatase

Answer

Calcium

Answer

Ferritin

Answer

Phosphorus

Question 2

Which hemoglobin has diagnostic value in diabetes mellitus?

Accepted Answer

HbA1c

Answer

HbA

Answer

HbF

Answer

HbS

Question 3

Which of the following biochemical markers is NOT elevated in a child presenting with jaundice, icterus, pruritus, and clay-colored stools?

Accepted Answer

Glutamate dehydrogenase

Answer

Gamma glutamyl transpeptidase

Answer

Alkaline phosphatase

Answer

5' nucleotidase

Question 4

Urobilinogen levels in obstructed jaundice due to gallstones will be:

Accepted Answer

Completely absent

Answer

Significantly elevated

Answer

Mildly elevated

Answer

Unchanged

Question 5

In a primary health care setting, which anticoagulant combination is recommended for sending blood samples for accurate blood glucose estimation?

Accepted Answer

Potassium oxalate + sodium fluoride

Answer

EDTA (Ethylenediaminetetraacetic acid)

Answer

Heparin (Unfractionated Heparin)

Answer

Potassium oxalate (alone)

Clinical Biochemistry — MCQs

Clinical Biochemistry — MCQs

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